<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      const arr = ["b", "c", "b", "c", "a", "b", "c"];

      const obj = {};
      // 你的代码 ...
      arr.filter(item=>{obj[item]})

      console.log(obj); // ==> {a：1， b: 3, c:  3}
    </script>
  </body>
</html>
